Concrete is a building material that is relatively widely used. Concrete made from cement, water, sand, and gravel. Cement prices are relatively expensive compared to the aggregate. In this study, volcanic ash and lime is used to partially replace cement material, given the nature pozollan volcanic ash that can react with lime. In this study are expected by the addition of volcanic ash and lime can increase the compressive strength of concrete and obtain mixing ratio that produces the highest compressive strength. Normal quality concrete compressive strength planned in this study was 27 MPa. In this study the composition of volcanic ash replacement of cement with 5% lime 25%, 10% volcanic ash lime 20%, 15% volcanic ash lime 15%, 20% volcanic ash lime 10%, and 25% lime ash 5% of the weight cement. Water-cement ratio determined on all variations of the same concrete mix that is of 0.54. Specimens used were cylindrical (30 cm high and 15 cm diameter) of 3 specimens for each variation and testing performed by the concrete compression test after reaching the age of 28 days. From research to replace as much as 30% of cement with volcanic ash and lime can increase the compressive strength of concrete, the concrete compressive strength concrete mix with highs in the replacement of cement with 15% ash and 15% lime (B3) of 38.065 MPa. On the compressive strength of the mixture is increased by 25.30% against the normal concrete. The increase was due to the addition of volcanic ash percentage balance and percentage additions of lime, so that the reaction occurs pozollan well.
Keyword : Volcanic Ash, Lime, Concrete Compressive Strength,